NYPD officers were swarmed by protesters in a knock-down, drag-out brawl on the Brooklyn Bridge on Saturday night that sent two police lieutenants to the hospital.

The melee broke out at the tail end of a daylong march — which drew nearly 30,000 protesters calling for justice in the wake of the police-involved deaths of civilians Michael Brown and Eric Garner — when a group of marchers swarmed officers as they tried to make an arrest on the bridge roadway around 7:15 p.m., cops said.

“Over the past few weeks, we have gone to great lengths to ensure, even facilitate, people’s ability to protest,” said Chief of Department James O’Neill on Saturday.

“I want to be clear that these assaults do not come with the territory,” he said.

The president of the NYPD Hispanic Society on Sunday demanded that Mayor de Blasio and the City Council “denounce these disgraceful protests calling for dead police officers.

“Many elected officials are quick to speak out against police officers, but now that we need them to calm our city, where is their press conference on the steps of City Hall?” said the leader, Dennis Gonzalez. “Their silence is deafening. Tweets about non-violence and peaceful protests aren’t good enough.”

Demonstrators march in New York on Dec. 13, 2014, during the Justice for All rally and march.

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Demonstrators march in New York to protest the deaths of Michael Brown in Ferguson, Mo., and Eric Garner, in New York City, by police officers.

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R. Umar Abbasi

R. Umar Abbasi

R. Umar Abbasi

R. Umar Abbasi

R. Umar Abbasi

Several hundred marchers from the Eric Garner protest crossed the Brooklyn Bridge.

William Farrington

Thousands of people join the Millions March protesting the police killing of Eric Garner.

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De Blasio released a statement Saturday in which he first talked about how “peaceful” city protesters have been.

“The people of New York have provided an example to the world on how to protest, march and express themselves in a peaceful and respectful manner,” the mayor said.

He then added that “a small group of protesters allegedly assaulted some members of the NYPD.

“Let us be clear: there is no place whatsoever for violence of any kind, whether against the police or against our fellow citizens, in New York City,” de Blasio said. “We will not allow a small contingent of agitators to bring disorder and violence to these protests.”

The violence erupted shortly after the two lieutenants attempted to stop one of the angry agitators from hurling a garbage can at other cops standing in the walkway below, police said.

Protesters marched through the inbound traffic on the Brooklyn Bridge on Saturday night.AP

That’s when other demonstrators intervened and attacked the officers — knocking them to the ground and kicking and punching them before trying to steal their jackets and radios, according to police.

“[The officers] were punched by numerous people,” said Deputy Commissioner of Intelligence and Counter Terrorism John lMiller. “They were kicked in their face and in the head while the group attempted to steal their portable radios and tear away their police identification jackets.”

The protester who tried to throw the garbage can fled but left behind a bag containing three hammers and a black ski mask, cops said.

The lieutenants, each assigned to the department’s Legal Bureau, were rushed to an undisclosed hospital where one was treated for a broken nose, police said. Their injuries were not life-threatening.

“This is relatively common in our experience with groups that operate within the protesters, who seek out confrontations,” Miller said. “They put the masks on, they use hammers, wrenches, and other objects to either commit assaults or property damage.”